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 Post subject: Help diagnosing tremolo issue in Fender amp?
PostPosted: Nov Wed 15, 2017 7:13 pm 
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Joined: Jan Thu 24, 2013 11:50 pm
Posts: 2630
Location: Bristol, Rhode Island
Hi all,

I am having a problem I cannot sort out in a Fender 6G3 circuit I am building. the problem is I get ZERO tremolo effect when the amp is playing. However I can hear the tremolo loud and clear but ONLY when I kill the power. As soon as the caps start discharging, and before they discharge completely and the voltage is gone I can hear the tremolo clear as a bell.

I have troubleshooted this non-functioning tremolo for a few days now. I have checked and rechecked the circuit, all parts, all wiring, etc. All voltages in the amp are right on spec. Any ideas on how to go about fixing this issue? Thanks!

https://robrobinette.com/images/Guitar/ ... l_Path.gif


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 Post subject: Re: Help diagnosing tremolo issue in Fender amp?
PostPosted: Nov Wed 15, 2017 8:55 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 16836
Location: Albuquerque, NM 87123
Is your -26 volts there?


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 Post subject: Re: Help diagnosing tremolo issue in Fender amp?
PostPosted: Nov Wed 15, 2017 11:28 pm 
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Joined: Jan Thu 24, 2013 11:50 pm
Posts: 2630
Location: Bristol, Rhode Island
Oh yes. I'm getting good voltage everywhere throughout the set. Bias voltage around 27 percent and voltages are reight on spec everywhere else.


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 Post subject: Re: Help diagnosing tremolo issue in Fender amp?
PostPosted: Nov Thu 16, 2017 3:46 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 16836
Location: Albuquerque, NM 87123
I'm always suspicious when someone says "I've checked everything and it still doesn't work." You missed something, probably in that triode tremolo circuit.


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 Post subject: Re: Help diagnosing tremolo issue in Fender amp?
PostPosted: Nov Thu 16, 2017 3:37 pm 
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Joined: Aug Sun 23, 2015 6:01 pm
Posts: 532
Location: South Jersey East of Philly
Have you re-capped and checked resistor values on the entire trem circuit? If you're getting some tremolo on shut down when the voltage is going down, that shows something is out of spec.


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 Post subject: Re: Help diagnosing tremolo issue in Fender amp?
PostPosted: Nov Thu 16, 2017 4:36 pm 
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Joined: May Sat 06, 2006 4:03 am
Posts: 2817
Location: ZIP 23831 South of Richmond, VA 25 miles down the pike.
Did you 3-prong the power cord and remove that ground switch? Also your tremolo petal switch if used and/or plug and jack are wired or shorting wrong.

Bill J.


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 Post subject: Re: Help diagnosing tremolo issue in Fender amp?
PostPosted: Nov Sat 18, 2017 8:44 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 2054
Location: New Port Richey, FL, USA
He said that he's building it, not fixing one. So re-capping and new cord wouldn't apply here.

I know you've double checked everything, but give it one more go. In particular your capacitors. The tremolo works by causing the bias of the output tubes to fluctuate up and down. It's sounds like there's a capacitor that's filtering that out. It's acting just like the filter cap in the power supply. If it is a cap in the wrong place filtering the tremolo output, then it would no longer be able to charge up once the power is cut.

Make sure too that the .05uF cap right at the intensity pot is the correct value. With today's parts, you would use a .047, but make sure you didn't end up something like a 4.7uf. I would think that would be a hard mistake to make, but looking at the schematic, it looks like that would easily cause the problem.

It's very easy when you are very intently checking and rechecking, to miss an obvious detail that's right there in front of you. I'd say all of us here have done so at one time or another.

_________________
Michael


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